Many retractable safety barriers for doorways have been developed to help prevent children and pets from entering certain areas. To selectively open or block a doorway, some barriers include a rollup panel that can be unrolled to extend across and block the doorway. When not in use or to allow passage, the panel can wrap about a roller for storage along one side of the doorway. A few examples of retractable barriers with rollup panels are disclosed in U.S. Pat. Nos. 5,636,679; 5,690,317; 6,536,502; 5,505,244; and 6,056,038.
Once such a rollup panel is extended across a doorway, usually some type of locking mechanism helps prevent the panel from unwrapping any farther so that the child or pet is unable to force the panel open. Such locking mechanisms typically include a little tab or pawl that engages a ratchet or some other type of tooth or slotted wheel, which in turn is coupled to the roller about which the panel is wrapped. The tab or pawl engaging the wheel hopefully prevents the roller from releasing the panel any farther. This may work well for light duty applications involving children and pets; however, such barriers do not appear adequate for industrial applications.
In factories, for example, a forklift and other material handling equipment may need to travel near operating equipment such as machine tools (machining centers, turning centers, etc.). A permanent guardrail may prevent a forklift from striking the machine, but the guardrail may also interfere with material handling equipment trying to load and unload the machine of its work pieces. While a permanent guardrail may be effective at preventing a forklift from striking a machine, forklift impact with a traditional, rigid guardrail often results in significant and permanent damage to the guardrail.
Truck loading docks may also have a need for a retractable barrier. A barrier may help prevent dockworkers and material handling equipment from accidentally falling off the edge of the dock's elevated platform. The platform's height is about the same as that of an average truck bed. Although a door typically exists at the edge of the platform, the door's strength may be insufficient to withstand the impact of a forklift, or the door may be left open for various reasons. The door, for instance, may be left open simply because the weather is nice, and the workers inside would like to enjoy some fresh air. With the door open, however, the loading dock platform may create a safety problem.
Although costly massive safety gates have been used at loading docks, they can take up a lot of space even when they are opened to allow passage through the doorway. Even though they may be able to stop a slowly moving forklift, an impact can cause considerable damage to the gate due to the gate's limited ability to resiliently absorb the impact. Also, permanent or other conventional guarding may not be suitable for loading dock areas, as such guarding may interfere with operating the door, loading and unloading trucks, and operating a dock leveler that may be installed at the platform.
A dock leveler is often installed at the loading dock platform to compensate for a height difference that may exist between the platform and the bed of the truck. A dock leveler typically includes a deck that is hinged at its back edge to raise or lower its front edge to generally match the height of the truck bed. Often an extension plate or lip is pivotally coupled to the deck to bridge the gap between the deck's front edge and a back edge of the truck bed. The deck and extended lip provide a path for forklifts to travel between the loading dock platform and the truck bed, thus facilitating loading or unloading of the truck. Unfortunately, a conventional barrier or guardrail extending over the dock leveler may restrict the deck's upward pivotal motion.
Since a dock leveler and the adjacent door move in the area where guarding may be needed, it becomes challenging to provide the area with a barrier that is movable yet sufficiently strong to impede heavy material handling equipment. Moreover, some installations require a removable guardrail that can cover a particularly long span without intermediate support posts. Covering such a span, however, can make it difficult for a single person to manually extend and retract a long flexible barrier.